It is known from European patent EP 1017465-B and from European patent applications EP1438540-A and EP1499419-A to separate a fluid mixture in a fluid separator in which the fluid mixture is accelerated in a throat section of a flow channel, whereby the fluid mixture is expanded and cooled such that at least some initially gaseous components condense and at least some condensed components are subsequently removed from the fluid mixture in the flow channel at a location downstream of the throat section.
The separators known from European patent EP 1017465-B and from European patent application EP1438540-A are cyclonic separators with a substantially cylindrical flow channel in which the fluid mixture may be accelerated to a transonic or supersonic velocity and wherein a swirling motion is imposed on the accelerated fluid mixture by one or more swirl imparting vanes. In the cyclonic fluid separator known from European patent EP 1017465-B one or more swirl imparting vanes are arranged downstream from the throat section of the fluid channel and in the cyclonic fluid separator known from European patent application EP 1438540-A the swirl imparting vanes are arranged upstream of the throat section of the fluid channel.
European patent application EP 1499419-A discloses a separator wherein a spray of electrically charged droplets is injected into the separator, with a slit-shaped or tubular nozzle in which the fluid stream is accelerated to a transonic or supersonic velocity and thereby expanded and cooled. This separator has an electrostatic charged wall that attracts the electrically charged droplets, which serve as nucleation sources for other initially gaseous components of the multiphase fluid stream of which at least some become supersaturated when they are cooled within the nozzle.
Japanese patent publication JP10277355 discloses a method for removing contaminants from air that is blown into a clean room for manufacturing semiconductors, wherein a UV light source is used to enhance nucleation of contaminants. The air blower will not cool the air and a large air cooling unit is required to cool the air to such a temperature that condensation of water and other contaminants will occur. This known method therefore requires large pieces of equipment with a significant power consumption.
The article ‘Photoinduced nucleation in supersaturated mercury vapour’ published on 15 Jun. 1998 by H. Uchtmann, R. Dettmer, S. D. Barovskii and F. Hensel in the Journal of Chemical Physics, volume 108, number 23, discloses that the rate of nucleation is increased if a supersaturated mercury vapour is illuminated with electromagnetic radiation absorbed by the mercury vapour atoms. The experiments described in this article were carried out in an upward thermal diffusion chamber.
It is known from U.S. Pat. No. 6,663,690 to remove elemental mercury from emissions of coal-fired utilities by the selective ionisation of mercury atoms using ultraviolet radiation, followed by electrostatic precipitation of the mercury atoms.
In this known method the mercury atoms are excited by the ultraviolet radiation and then ionised using radiation of a different wavelength and then exposed to a supersaturated water vapour to produce charged droplets, which are accumulated and removed from the flux of flue gases at the bottom of the stack. The stack therefore serves as a liquid settling chamber in which the charged droplets are removed from a flux of upwardly moving flue gases of which the velocity is low enough to inhibit the charged droplets to be dragged upwards by the flue gas stream.
A disadvantage of the mercury removal methods known from U.S. Pat. No. 6,663,690 is that liquid settling chambers require that the fluid mixture passes at such a low velocity through the chamber that liquid components are allowed to migrate to and settle at the bottom of the separation chamber. The known methods therefore require use of large pieces of equipment.
It is an object of the present invention to provide a fluid separation method that does not require large gravity settling chambers.
It is a further object of the present invention to provide a fluid separation method in which excitation of a selected component enhances the condensation of said component and/or ionisation of a selected component generates condensation nuclei for other supersaturated fluid components, such as polar components, such that in addition to the bonding of ionised components in the liquid phase, also condensation of other components is enhanced.